Remove "from __future__" from airflow/providers __init__.py

[potiuk]

Cleans-up airflow and providers __init__.py files in order to get providers import work again.

This is done by excluding the two __init__.py files from automated ruff isort rules adding from __future__ import annotations.

Also removed the __init__.py file from "providers" directory, it is not needed there, because "providers" is just a folder where we keep provider files, it's not a Python package.

That should finally get rid of the Intellij teething import problem that has been introduced in #42505.

There were earlier - unsuccesful - attempts to fix it in the #43116 and #43081 that followed #42951 - but the key is that Pycharm requires the namespace's extend_path to be first "real" line of code in the __init__.py to understand that the package is an "explicit" namespace package - and it conflicts with the requirement of "from future import annotations" to be the first line of Python code.

Also this PR fixes a few other teething problems with setup of tests that were introcuded in #42505 and #43802 "masked" by having __init__.py added in providers package:

• common.sql interface pre-commit used wrong path to generated files
• openlineage extractor test that should not expect "providers.tests."
  but "tests." package
• common_sql_api_stubs wrongly calculating generated path for
  stub-generated files
• pytest_plugin expecting .asf.yml in "airflow" sources - even during
  compatibility tests with older version of airflow (where the
  .asf.yml is not present)

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[potiuk]

It nicely works for my IntelliJ:

[potiuk]

Ha.. Still some errors to fix but we get closer :) . Let me work on those :)

[potiuk]

I had to fix (I hope 🤞) a few other problems that wer "masked" by having "init.py" in providers folder.